title: [Screening for trisomy 21 by measuring nuchal translucency during the first trimester of pregnancy].
abstract: The purpose of the present literature review is to assess the screening value of trisomy 21 by measurement of fetal nuchal translucency (NT) thickness in the first trimester. NT is a subcutaneous translucency between the skin and the soft tissues overlying the cervical spine, which disappears in the second trimester. Ultrasound examination was used to image a sagittal section of the fetus to measure the maximum thickness of the subcutaneous translucency. NT is physiological for a measurement < 3 mm but the incidence of chromosomal abnormalities (essentially trisomies 21, 18 and 13) increases when NT > or = 3 mm. Differential diagnoses include cystic hygroma and fetal hydrops. For screening purposes, a cut-off threshold value of > or = 3 mm, with a standardized technique, gave a sensitivity > or = 50%, a false positive rate < 5% and a positive predictive value > 1%. In the chromosomally normal group, prognosis was good, but incidence of structural defects and fetal loss increased, with a sharp rise in these complications for fetal translucency thickness > or = 5 mm.
authors.affiliation: Centre de Diagnostic Anténatal et d'Explorations Fonctionnelles, Hôpital La Grave, Toulouse.
authors.forename: T
authors.initials: T
authors.lastname: Charasson
authors.forename: P
authors.initials: P
authors.lastname: Ko-Kivok-Yun
authors.forename: F
authors.initials: F
authors.lastname: Martin
authors.forename: M F
authors.initials: MF
authors.lastname: Sarramon
mesh_terms: D000886:Anthropometry / Q000379:methods*; D003937:Diagnosis, Differential; D004314:Down Syndrome / Q000000981:diagnostic imaging* / Q000473:pathology*; D005260:Female; D006801:Humans; D015994:Incidence; D008403:Mass Screening / Q000379:methods*; D009333:Neck / Q000473:pathology*; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016216:Ultrasonography, Prenatal / Q000379:methods*
vernacular_title: Dépistage de la trisomie 21 par mesure de la clarté nucale au premier trimestre de la grossesse.